1H-pyrazolo[1,5-b][1,2,4]triazole magenta couplers are disclosed in JP-A 59-171956 and U.S. Pat. No. 4,540,654. (The term "JP-A" as used herein means an "unexamined published Japanese patent application".) These couplers are known to have excellent color reproducibility and give fast color images and they are also known to be produced easily. 6-Oxygen-substituted 1H-pyrazolo[1,5-b][1,2,4]-triazole couplers having improved sensitivity and gradation are disclosed in JP-A-62-209457 and European Patent Laid-Open No. 226849. The split-off group of the couplers specifically illustrated in the specifications is a halogen atom, an arylthio group, an aryloxy group or a phthalimido group. The couplers have a drawback in that they are unstable to heat. Of these known couplers, those having an arylthio split-off group are stable, but this group, when split off therefrom by coupling with an oxidation product of an aromatic primary amine or by color development of them, has a harmful influence on silver halides. Therefore, it is indispensably necessary to increase the molecular weight of the couplers, which, however, is inconvenient especially to the sharpness of picture-taking photographic materials. For the purpose of obtaining a sufficient sharpness of picture-taking photographic materials, incorporation of couplers having high color forming capacity, i.e., the capacity for forming satisfactory color images into them, is desired. In this respect, the known couplers are insufficient and unsatisfactory.
JP-A-2-59584 mentions production of 6-oxygen-substituted 1H-pyrazolo[1,5,-b][1,2,4]triazole couplers having a pyrazolyl group as the split-off group. However, these couplers interact with silver halides, and therefore have a drawback in that they lower the sensitivity of photographic materials. In addition, they have another drawback in that the magenta dyes to be formed therefrom by color development are often broadened.